leds: trigger: netdev: rename 'hw_control' sysfs entry to 'offloaded'

Commit b655892f ("leds: trigger: netdev: expose hw_control status
via sysfs") exposed to sysfs the flag that tells whether the LED trigger
is offloaded to hardware, under the name "hw_control", since that is the
name under which this setting is called in the code.

Everywhere else in kernel when some work that is normally done in
software can be made to be done by hardware instead, we use the word
"offloading" to describe this, e.g. "LED blinking is offloaded to
hardware".

Normally renaming sysfs entries is a no-go because of backwards
compatibility. But since this patch was not yet released in a stable
kernel, I think it is still possible to rename it, if there is
consensus.

Fixes: b655892f

 ("leds: trigger: netdev: expose hw_control status via sysfs")
Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20230821121453.30203-1-kabel@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>